On optimisation of N2 and CO2-selective hybrid membrane process systems for post-combustion CO2 capture from coal-fired power plants

A superstructure-based optimisation model for the CO2 capture process using an N-2 -selective and CO2-selective membranes is presented. The model automatically selects either of the membranes for each membrane stage to have a hybrid membrane CO2 capture process. The superstructure embeds numerous process routes and allows the collection of product streams and residue streams from either the retentate side or permeate side of the multi-membrane stages. This results in novel process flowsheets for post-combustion CO2 capture using membrane technology. In the study, the optimisation of carbon capture by an all N-2-selective membrane process is also carried out. At 90% recovery and 95% product purity, the multi-stage optimisation of the N-2-CO2 hybrid membrane process reduces the total membrane area by 46% and the cost of capture by 14% compared to the optimised CO2-selective membrane process.